Packaged microelectronic devices and related connection components, such as interposers or the like, use various structures to facilitate attachment with other packaged microelectronic devices or connection components to form various microelectronic assemblies. Such structures can include contact pads in the form of enlarged areas of a conductive metal exposed at surfaces of the devices or components. Alternatively, such structures can be in the form of exposed ends of metalized vias, conductive pins, posts, or the like. When aligned with similar connection features in another device or component, the connection features can be joined together using, for example, a conductive joining material, such as a solder mass or the like. Solder masses, such as solder mass 1 shown in FIG. 1A are often used to form such joints because they can be easy to join between structures due to their relatively low melting temperature. Further, such conductive joining masses can be reworkable or reflowable, allowing repair or adjustment of joints.
The use of such joining masses can have some deficiencies, however, in particular such joints, when melted in order to form joints between, for example, contact pads or the like, can undergo lateral deformation. This can be exhibited in widening of the masses prior to cooling, resulting in joints that are wider than the initially-deposited masses. Further, such widening can increase during normal use of the microelectronic assembly due to heating of the joints. As a result, as shown in FIG. 1C, it is generally accepted that a minimum spacing P between conductive connection elements, such as contact pads 2 (FIG. 1B) or the like, is equal to 1.5 times a width W of the conductive connection elements 2 themselves. Further, because the widths of conductive joining masses, such as those of solder or the like, are directly related to the heights thereof (due to surface tension during forming, which takes place in a liquid state), the higher a desired height of such a joint, the greater the width. This relationship can necessitate large contact pads 2 and large pitch P based solely on a desired bond height.
The need for relatively larger contact pads 2 or other connection features can result in increased dishing along bonding surfaces 3 of these features. In particular, when the surfaces of microelectronic devices or connection components are finished by polishing (by chemical or mechanical means), the connection features can develop a concavity. Such concavity can be increased in relatively larger features. This dishing can adversely affect bond strength and is generally not desirable.